The problems posed by substances that deplete the atmospheric ozone layer were dealt with in Montreal, where the protocol was signed, decreeing a reduction in the production and use of chlorofluorocarbons (CFCs). This protocol has been subject to amendments which ordered the abandonment of CFCs and extended the regulation to other products including hydrochlorofluorocarbons (HCFCs).
The refrigeration and air conditioning industry has heavily invested in substitutions for these refrigerant fluids and thus hydrofluorocarbons (HFC) have been commercialized.
In the automotive industry, air conditioning systems for vehicles sold in numerous countries have gone from a chlorofluorocarbon-based (CFC-12) refrigerant fluid to one which is hydrofluorocarbon-based (1,1,1,2-tetrafluoroethane: HFC-134a), which is less harmful to the ozone layer. However, in light of the objectives set by the Kyoto protocol, HFC-134a (GWP=1430) is considered to have a high warming power. A fluid's contribution to the greenhouse effect is quantified by a criterion, GWP (Global Warming Potential) which sums up the warming power by giving a reference value of 1 to carbon dioxide.
Hydrofluoroolefins (HFO) have a relatively low warming power and therefore meet the objectives set by the Kyoto protocol. Document JP 4-110388 discloses hydrofluoropropenes as heat-transfer agent.
In the industrial field, the most commonly used refrigerant machines are based on cooling by evaporation of a liquid refrigerant fluid. After vaporization, the fluid is compressed then cooled in order to return to the liquid state and thus continue the cycle.
The refrigeration compressors used are of the reciprocating, scroll, centrifugal or screw type. In general, internal lubrication of the compressors is essential in order to reduce wear and heating of the moving members, complete their leaktightness and protect them against corrosion.
In addition to good heat-transfer agent properties, in order for a refrigerant fluid to be commercially accepted, it must especially exhibit thermal stability and compatibility with lubricants. Indeed, it is highly desirable for the refrigerant fluid to be compatible with the lubricant used in the compressor, present in the majority of refrigeration systems. This combination of refrigerant fluid and lubricant is important for the implementation and the efficiency of the refrigeration system; the lubricant should especially be sufficiently soluble or miscible in the refrigerant fluid over the entire operating temperature range.
There is therefore a need to find novel refrigerant fluid and lubricant pairs which especially are thermally stable and which are able to be used in refrigeration, air conditioning and heat pumps.